1. Field of the Invention
This invention generally relates to quick disconnect valve couplings and more particularly to locking means for isolating spring forces of spring loaded anti-checking valve couplings connectable under high fluid pressure and spring forces.
2. Description of the Prior Art
Generally, valved quick disconnect couplings used for interconnecting fluid conveying conduits are of the spring loaded type; that is, each of the two members of the coupling includes a spring for urging a valve therein to a closed or seated position when it is disconnected. Conventionally, couplings that connect under pressure include spring means for biasing and holding the valves in their open or unseated position when they are interconnected or coupled together. The couplings must be capable of transmitting fluid under high pressure such as would be encountered on modern-day tractors and related fluid pressure operated implements. Inasmuch as the fluid flowing through these couplings is at a relatively high pressure, it is apparent that the spring or springs employed for urging the valves to an open position and holding them thereat must have a very high compressive strength, particularly when surges of high fluid pressure occur from the implement side of the coupling. At such times, the surge of fluid pressure acting on the valves may equal or exceed the strength of the springs and either one or both valves of the coupling may inadvertently close. The inadvertent closure of the valves during use may cause considerable damage to the fluid operating system of a tractor and/or implement or become inoperative until the pressure in the system is relieved which, of course, may result in expensive repairs, and loss of production time.
To connect a coupling of this type, an operator is required to manually push one coupling member into the other and overcome the strength of the spring or springs which urge the valves into their seated position, as well as compress the springs which hold the valves in their open or unseated position. Thus, when springs of sufficient strength are employed to hold the valves in their open position against surges of high fluid pressure, it may be difficult, if not impossible, to manually compress the springs and effect connection of the coupling members.
From the foregoing discussion, it is apparent that the greater the compressive strength or urging effect of the spring in holding the valves in an open position, the more effective the coupling is for conveying fluid under high flow. However, the magnitude of the urging action of the spring must be based on the minimum force with which it is desired to have the valves held in their open position while taking into consideration the effort that must be expended by an operator in connecting the members of the coupling together.
Attempts have been made in the past to reduce the required strength of such springs by providing some type of inhibiting device between the reaction member and the spring means which holds both valves in their open position. An example of one such device is shown in U.S. Pat. No. 3,477,468, issued on Nov. 11, 1969. In the patent disclosure, a spring biased detent ball is disposed between a stationary member and a spring urged reaction member which moves and holds the valves of the coupling in their open positions. This, of course, permits use of lighter weight springs than those normally found in such couplings. However, an undesirable feature of this type of coupling is that the force required to shear the detent ball from the stationary member is not of great magnitude, and thus the strength of the springs holding the valves in an open position cannot be greatly reduced.